The present invention relates to a semiconductor thin film photoelectric converter and a transparent laminated body used therefor, and more particularly to improvements in the performance of a hybrid-type thin film photoelectric converter as well as a transparent laminated body which can preferably be used therefor.
A semiconductor thin film photoelectric converter generally includes a first electrode, one or more semiconductor thin film photoelectric conversion units and a second electrode, successively laminated on a substrate having an insulating surface. One photoelectric conversion unit includes an i-type layer sandwiched by a p-type layer and an n-type layer. The i-type layer making up a major portion of a thickness of the photoelectric conversion unit is a substantially intrinsic semiconductor layer, mainly in which photoelectric conversion occurs.
Accordingly, the photoelectric conversion unit, no matter whether p and n conductivity type layers contained therein are amorphous or crystalline, will be referred to as an amorphous unit if a photoelectric conversion layer of i-type is amorphous, or referred to as a crystalline unit if the same is crystalline. Note that in this specification, the term xe2x80x9ccrystallinexe2x80x9d also refers to those which partially include amorphous states, as commonly used in the technical field of the thin film photoelectric converter.
On the other hand, a p or n type conductivity type layer serves to produce a diffusion potential within the photoelectric conversion unit. Open-circuit voltage, which is one of important properties of the photoelectric converter, varies depending on a magnitude of the diffusion potential. These conductivity type layers, however, are inactive layers not directly contributing to photoelectric conversion, and light absorbed by impurities doped in the conductivity type layer will become a loss, not contributing to power generation. Therefore, the conductivity type layer is desirably minimized in thickness, on the precondition of producing a required diffusion potential.
When the thin film photoelectric converter is formed on a transparent insulating substrate such as a glass plate, the substrate can serve as a cover glass for surface protection of the photoelectric converter. Generally, a p-type layer having a relatively large band gap, an i-type photoelectric conversion layer, and an n-type layer having a relatively small band gap are successively laminated on a transparent electrode formed on the glass substrate.
As a method of improving conversion efficiency of the thin film photoelectric converter, more than one photoelectric conversion units are stacked to constitute a tandem-type converter. In this method, a front unit including a photoelectric conversion layer having a large band gap is arranged on a light incident side of the photoelectric converter, and behind the same, a rear unit including a photoelectric conversion layer (made of Sixe2x80x94Ge alloy, for example) having a small band gap is successively arranged. This enables photoelectric conversion in a wide wavelength range of incident light, and thus conversion efficiency of the entire converter is improved. Among the tandem-type thin film photoelectric converters, one including both an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit stacked is called a hybrid-type thin film photoelectric converter.
For example, an i-type amorphous silicon can photoelectrically convert light having a wavelength of up to about 800 nm on a longer wavelength side, while an i-type crystalline silicon can photoelectrically convert light having a wavelength of up to about 1100 nm, which is longer than the former. Accordingly, when the hybrid-type thin film photoelectric converter is formed on the glass substrate, a transparent electrode, at least one amorphous unit, at least one crystalline unit and a backside electrode are stacked thereon in this order.
Such a hybrid-type thin film photoelectric converter can exhibit a significantly higher photoelectric conversion efficiency than a single-type thin film photoelectric converter including either a single amorphous photoelectric conversion unit or a single crystalline photoelectric conversion unit. The hybrid-type thin film photoelectric converter with such a high performance, however, is still considered to have a room for further improvement in the performance.
An object of the present invention is to provide a hybrid-type thin film photoelectric converter having a further improved photoelectric conversion property as well as a transparent laminated body which can preferably be used therefor.
A hybrid-type thin film photoelectric converter according to one aspect of the present invention includes a transparent electrode, at least one amorphous photoelectric conversion unit, at least one crystalline photoelectric conversion unit and a backside electrode, successively stacked on a transparent glass substrate. The transparent electrode has a thickness of more than 400 nm and less than 1000 nm. A transparent laminated body consisting of the glass substrate and the transparent electrode has a haze ratio of more than 2% and less than 10%.
In such a hybrid-type thin film photoelectric converter, preferably, the amorphous photoelectric conversion unit has a thickness of more than 80 nm and less than 350 nm, and the crystalline photoelectric conversion unit has a thickness of more than 1 xcexcm and less than 5 xcexcm.
A crystalline photoelectric conversion layer included in the crystalline photoelectric conversion unit preferably includes a columnar crystal structure along a direction of thickness thereof. In addition, the columnar crystal preferably extends preferentially along a crystal direction  less than 110 greater than .
The backside electrode preferably includes a transparent conductive oxide layer and a metal layer successively laminated. The transparent conductive oxide layer preferably has a thickness of more than 70 nm and less than 100 nm.
The photoelectric conversion layers included in the amorphous photoelectric conversion unit and the crystalline photoelectric conversion unit can be formed with silicon or silicon-germanium alloy.
A transparent laminated body according to another aspect of the present invention is provided for use in the hybrid-type thin film photoelectric converter as described above. The transparent laminated body includes a glass substrate and a transparent conductive layer formed thereon having a thickness of more than 400 nm and less than 1000 nm, and has a haze ratio of more than 2% and less than 10%.